Power control protocol for highly variable data rate reverse link of wireless communication system

ABSTRACT

A subscriber unit performs power control of a reverse link by sending heartbeat messages to a base station, permitting the base station to determine a reverse link quality report. Using a reverse link quality report message received from the base station, the subscriber unit calculates its reverse power level and maintains the reverse power level during the standby state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/763,747, filed Apr. 20, 2010, which is a continuation of U.S.application Ser. No. 11/706,463, filed Feb. 13, 2007, now U.S. Pat. No.7,701,903, which is a continuation of U.S. application Ser. No.11/250,727, filed Oct. 14, 2005, now U.S. Pat. No. 7,184,417 which inturn is a continuation of U.S. application Ser. No. 09/158,421, filedSep. 21, 1998, now U.S. Pat. No. 6,956,840, which are all incorporatedby reference as if fully set forth.

BACKGROUND

The increasing use of wireless telephones and personal computers has ledto a corresponding demand for advanced telecommunication services thatwere once thought to only be meant for use in specialized applications.In the 1980's, wireless voice communication became widely availablethrough the cellular telephone network. Such services were at firsttypically considered to be the exclusive province of the businessmanbecause of expected high subscriber costs. The same was also true foraccess to remotely distributed computer networks. Until very recently,only business people and large institutions could afford the necessarycomputers and wireline access equipment. As a result of the widespreadavailability of both technologies, the general population nowincreasingly wishes to not only have access to networks such as theInternet and private intranets, but also to access such networks in awireless fashion as well. This is particularly of concern for the usersof portable computers and laptops.

There still is no widely available satisfactory solution for providinglow cost, high speed access to the Internet, private intranets, andother networks using the existing cellular wireless infrastructure. Thissituation is most likely an artifact of several unfortunatecircumstances. For one, the typical manner of providing high speed dataservice in the business environment over the wireline network is notreadily adaptable to the voice grade service available in most homes oroffices. Such standard high speed data services also do not lendthemselves well to efficient transmission over standard cellularwireless handsets. Furthermore, the existing cellular network wasoriginally designed only to deliver voice services. As a result, theemphasis in present day digital wireless communication schemes lies withvoice, although certain schemes such as IS-95B do provide some measureof asymmetrical behavior for the accommodation of data transmission. Forexample, the data rate on an IS-95B forward traffic channel can beadjusted in increments from 1.2 kbps up to 9.6 kbps for so-called RateSet 1 and in for increments from 1.8 kbps up to 14.4 kbps for Rate Set2. On the reverse link traffic channel, however, the data rate is fixedat 4.8 kbps.

Existing systems therefore typically provide a radio channel which canaccommodate maximum data rates only in the range of 14.4 kilobits persecond (kbps) at best in the forward direction. Such a low data ratechannel does not lend itself directly to transmitting data at rates of28.8 or even 56.6 kbps that are now commonly available using inexpensivewireline modems, not to mention even higher rates such as the 128 kbpswhich are available with Integrated Services Digital Network (ISDN) typeequipment. Data rates at these levels are rapidly becoming the minimumacceptable rates for activities such as browsing web pages. Other typesof data networks using higher speed building blocks such as the DigitalSubscriber Line (xDSL) service are also now coming into use in theUnited States.

Although such networks were known at the time that cellular systems wereoriginally deployed, for the most part, there is no provision forproviding higher speed data services over cellular network topologies.Unfortunately, in wireless environments, access to the channels bymultiple subscribers is expensive and there is competition for them.Whether the multiple access is provided by the traditional FrequencyDivision Multiple Access (FDMA) using analog modulation on a group ofradio carriers, or by newer digital modulation schemes the permitsharing of a radio carrier using Time Division Multiple Access (TDMA) orCode Division Multiple Access (CDMA), the nature of the radio spectrumis that it is a medium that is expected to be shared. This is quitedissimilar to the traditional environment for data transmission, inwhich the wireline bandwidth is relatively wide, and is therefore nottypically intended to be shared.

CDMA type multiple access schemes are generally thought to, in theory,provide the most efficient use of the radio spectrum. CDMA schemes onlywork well, however, when the power levels of individual transmissionsare carefully controlled. Present day CDMA wireless systems such asIS-95B use two different types of power control on the uplink in orderto ensure that a signal from a given subscriber unit arriving at thebase station does not interfere in a disruptive manner with the signalsarriving from other subscriber units. In a first process, referred to asopen loop power control, a rough estimate of the proper power controllevel is established by the mobile subscriber unit itself. Inparticular, after a call is established and as the mobile moves aroundwithin a cell, the path loss between the subscriber unit and the basestation will continue to change. The mobile continues to monitor thereceive power and adjust its transmit power. In particular, the mobilemeasures a power level on the forward link signal as received from thebase station and then sets its reverse link power accordingly. Thus, forexample, if the receive power level is relatively weak, then the mobileassumes that it is relatively distant from the base station andincreases its power level. The converse is true, in that a signalreceived at a relatively high level indicates that the mobile isrelatively close to the base station and therefore should betransmitting with reduced power.

Since the forward and reverse links are on different frequencies,however, open loop power control is inadequate and too slow tocompensate for fast Rayleigh fading. In other words, since Rayleighfading is frequency dependent, open loop power control alone cannotcompensate for it completely in CDMA systems.

As a result, closed loop power control is also used to compensate forpower fluctuations. In the closed loop process, once the mobile obtainsaccess to a traffic channel and begins to communicate with the basestation, the base station continuously monitors the received power levelon the reverse link. If the link quality begins deteriorating, the basestation sends a command to the mobile via the forward link to increaseits power level. If the link quality indicates excess power on thereverse link, the base station commands the mobile unit to power down.

In the IS-95B standard, the base station sends such power controlcommands to the mobile using a specially encoded message sent on aforward link traffic channel. These embedded messages contain powercontrol commands in the form of so-called power control bits (PCBs). Theamount of power increase and power decrease per each bit is nominallyspecified at +1 dB and −1 dB. The response of the mobile to these powercontrol bits is typically expected to be very fast in order tocompensate for fast Rayleigh fading. For this reason, these bits aredirectly sent over the traffic channel. In particular, certain selectedbits from the baseband stream are inserted or “punctured” into thetraffic stream to provide a separate power control sub-channel at a rateof 800 bits per second. The mobile unit thus continuously receives powercontrol bits every 1.25 ms via such bit “puncturing.”

SUMMARY

There recently have been developed certain optimizations of CDMA systemsfor data transmission. These systems use certain coded phase channelallocation schemes that take away coded phase channels when they are notin use and then reassign them to provide more efficient use of the radiospectrum. Ideally, coded phase channels may be allocated as rapidly aspossible to different connections while minimizing radio frequencysignaling needed. However, a virtual connection must remain open betweeneach mobile unit and the base station whether a coded phase channel isin use or not. Otherwise, it is necessary to reacquire synchronization,for example, each time that a channel is allocated or deallocated from aparticular connection.

Unfortunately, especially for the case of attempting to implement theclosed loop power control signaling, there is no active traffic channelin which to embed power control bits every 1.25 milliseconds (ms). Itwould be impractical to have to reacquire the proper power level eachtime that a new code phase channel is allocated.

It is therefore desirable to maintain the proper power level on thereverse link even as code phase channels are deallocated from aparticular connection.

The present invention is a technique for implementing a code divisionmultiple access system which dynamically assigns coded traffic channelson a demand basis. The technique maintains a known transmit power levelfor the reverse link channel equipment even when the subscriber unit hasentered a standby mode in which no traffic channels are active.

This is accomplished in the standby mode by having the base stationmeasure certain quality parameters of a maintenance heartbeat signalwhich is periodically sent on a reverse channel by a subscriber unitwhen in standby mode. The heartbeat signal is a minimal signal sent at arate which is only sufficient to maintain code phase lock between thesubscriber unit and the base station. The rate at which heartbeatsignals are sent depends upon the maximum expected rate of physicalmovement of the subscriber unit. For example, in systems expected tosupport walking speed-type mobility, the heartbeat signal need only besent every few seconds.

The link quality parameters are preferably a bit error rate measurement,but may also be a noise level measurement or signal power levelmeasurement.

The link quality information is then sent from the base station to thesubscriber unit typically formatted as a link quality report message.The link quality reports are sent on a forward link paging or syncchannel to a subscriber unit in standby mode.

The subscriber unit then uses the link quality information as oneparameter to a decision logic circuit or function which ultimatelydetermines the transmit power level for the associated reverse link.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views.

FIG. 1 is a block diagram of a wireless communication system making useof a bandwidth management scheme according to the invention.

FIG. 2 is a diagram showing how subchannels are assigned within a givenradio forward link frequency (RF) channel.

FIG. 3 is a diagram showing how subchannels are assigned within a givenreverse link RF channel.

FIG. 4 is a state diagram for a link quality messaging scheme accordingto the invention.

DETAILED DESCRIPTION

Turning attention now to the drawings more particularly, FIG. 1 is ablock diagram of a system 100 for providing high speed data and voiceservice over a wireless connection by seamlessly integrating a digitaldata protocol such as, for example, Integrated Services Digital Network(ISDN), with a digitally modulated wireless service, such as CodeDivision Multiple Access (CDMA).

The system 100 consists of two different types of components, includingsubscriber units 101-1, 101-2, . . . , 101-u (collectively, thesubscriber or mobile units 101) and one or more base stations 170. Thesubscriber units 101 and base stations 170 cooperate to provide thefunctions necessary in order to provide wireless data services to aportable computing device 110 such as a laptop computer, portablecomputer, personal digital assistant (PDA) or the like. The base station170 also cooperates with the subscriber units 101 to permit thetransmission of data between the subscriber unit and the Public SwitchedTelephone Network (PSTN) 180.

More particularly, data and/or voice services are also provided by thesubscriber unit 101 to the portable computer 110 as well as one or moreother devices such as telephones 112-1, 112-2 (collectively referred toherein as telephones 112). The telephones 112 themselves may in turn beconnected to other modems and computers which are not shown in FIG. 1.In the usual parlance of ISDN, the portable computer 110 and telephones112 are referred to as terminal equipment (TE). The subscriber unit 101provides the functions referred to as a Network Termination Type 1(NT-1). The illustrated subscriber unit 101 is in particular meant tooperate with a so-called basic rate interface (BRI) type ISDN connectionthat provides two bearer or “B” channels and a single data or “D”channel with the usual designation being 2B+D.

The subscriber unit 101 itself consists of an ISDN modem 120, a devicereferred to herein as the protocol converter 130 that performs thevarious functions according to the invention including spoofing 132 andbandwidth management 134, a CDMA transceiver 140, and subscriber unitantenna 150. The various components of the subscriber unit 101 may berealized in discrete devices or as an integrated unit. For example, anexisting conventional ISDN modem 120 such as is readily available fromany number of manufacturers may be used together with existing CDMAtransceivers 140. In this case, the unique functions are providedentirely by the protocol converter 130 which may be sold as a separatedevice. Alternatively, the ISDN modem 120, protocol converter 130, andCDMA transceiver 140 may be integrated as a complete unit and sold as asingle subscriber unit device 101. Other types of interface connectionssuch as Ethernet or PCMCIA may be used to connect the computing deviceto the protocol converter 130.

The ISDN modem 120 converts data and voice signals between the terminalequipment 110 and 112 to format required by the standard ISDN “U”interface. The U interface is a reference point in ISDN systems thatdesignates a point of the connection between the network termination(NT) and the telephone company.

The protocol converter 130 performs spoofing 132 and basic bandwidthmanagement 134 functions. In general, spoofing 132 consists of insuringthat the subscriber unit 101 appears to the terminal equipment 110, 112that is connected to the public switched telephone network 180 on theother side of the base station 170 at all times. The bandwidthmanagement function 134 is responsible for allocating and deallocatingCDMA radio channels 160, including management of the total bandwidthallocated to a given session by dynamically assigning sub-portions ofthe CDMA radio channels 160 in a manner which is also more fullydescribed below.

The CDMA transceiver 140 accepts the data from the protocol converter130 and reformats this data in appropriate form for transmission througha subscriber unit antenna 150 over CDMA radio link 160-1. The CDMAtransceiver 140 may operate over only a single 1.2288 MHz radiofrequency channel or, alternatively, in a preferred embodiment, may betunable over multiple ones of such channels.

CDMA signal transmissions are then received and processed by the basestation equipment 170. The base station equipment 170 typically consistsof multichannel antennas 171, multiple CDMA transceivers 172, and abandwidth management functionality 174. Bandwidth management 174controls the allocation of CDMA radio channels 160 and subchannels, in amanner analogous to the subscriber unit 101. The base station 170 thencouples the demodulated radio signals to the Public Switch TelephoneNetwork (PSTN) 180 in a manner which is well known in the art. Forexample, the base station 170 may communicate with the PSTN 180 over anynumber of different efficient communication protocols such as primaryrate ISDN, or other LAPD based protocols such as IS-634 or V5.2.

Continuing to refer to FIG. 1 briefly, bandwidth management 134 and 174therefore involve having the CDMA transceiver 140 loop back data bitsover the ISDN communication path to spoof the terminal equipment 110,112 into believing that a sufficiently wide wireless communication link160 is continuously available. However, only when there is actually datapresent from the terminal equipment to the wireless transceiver 140 iswireless bandwidth allocated. Therefore, a network layer connection neednot allocate the assigned wireless bandwidth for the entirety of thecommunications session. That is, when data is not being presented uponthe terminal equipment to the network equipment, the bandwidthmanagement function 134 deallocates initially assigned radio channelbandwidth 160 and makes it available for another transceiver and anothersubscriber unit 101.

It should also be understood that data signals travel bidirectionallyacross the CDMA radio channels 160. In other words, data signalsreceived from the PSTN 180 are coupled to the portable computer 110 in aso-called forward link direction, and data signals originating at theportable computer 110 are coupled to the PSTN 180 in a so-called reverselink direction. The present invention involves in particular the mannerof implementing a power control mechanism for the reverse link channels.

In order to better understand how bandwidth management 134 and 174accomplish the dynamic allocation of radio channels, turn attention nowto FIG. 2. This figure illustrates one possible frequency plan for theforward wireless links 160 according to the invention. In particular, atypical transceiver 170 can be tuned on command to any 1.2288 MHzchannel within a much larger bandwidth, such as up to 30 MHz. In thecase of location in an existing cellular radio frequency bands, thesechannels are typically made available in the range of from 800 to 900MH_(Z). For personal communication systems (PCS) type wireless systems,the channels are typically allocated in the range from about 1.8 to 2.0GigaHertz (GHz). In addition, there are typically two matching bandsactive simultaneously, separated by a guard band, such as 80 MHz; thetwo matching bands form the forward and reverse full duplex link.

Each of the CDMA transceivers, such as transceiver 140 in the subscriberunit 101, and transceivers 172 in the base station 170, are capable ofbeing tuned at any given point in time to a given radio frequencychannel. It is generally understood that, for example, a 1.2288 MHzradio frequency carrier provides, at best, a total equivalent of about500 to 600 kbps maximum continuous data rate transmission withinacceptable bit error rate limitations.

However, to make more efficient use of the available bandwidth, each1.2288 MHz radio channel on the reverse link is divided into arelatively large number of subchannels. In the illustrated example, thebandwidth is divided into sixty-four (64) subchannels 300, eachproviding an 8 kbps data rate. A given subchannel 300 is physicallyimplemented by encoding a transmission with one of a number of differentassignable pseudorandom codes and/or code phases. For example, the 64subchannels 300 may be defined within a single CDMA RF carrier by usinga different code phase for each defined subchannel 300.

As mentioned above, subchannels 300 are allocated only as needed. Forexample, multiple subchannels 300 are granted during times when aparticular ISDN subscriber unit 101 is requesting that large amounts ofdata be transferred. These subchannels 300 are quickly released duringtimes when the subscriber unit 101 is relatively lightly loaded.

The present invention relates in particular to maintaining the reverselink so that a transmit power level for the subchannels does not need tobe reestablished each time that subchannels are taken away and thengranted back.

FIG. 3 is a diagram illustrating the arrangement of how the subchannelsare assigned on the reverse link. It is desirable to use a single radiocarrier signal on the reverse link to the extent possible to conservepower as well as to conserve the receiver resources which must be madeavailable at the base station. Therefore, a single 1.2288 MHz channel350 is selected out of the available radio spectrum.

A relatively large number, N, such as 1000 individual subscriber unitsare then supported by using a single long pseudonoise (PN) code in aparticular way. First, a number, p, of phases of the code are selectedfrom an available 2⁴²−1 different code phases. The p code phase shiftsare then used to provide p subchannels. Next, each of the p subchannelsare further divided into s time slots. Therefore, the maximumsupportable number of supportable subscriber units, N, is p times s. Useof the same PN code with different phases and time slots provides manydifferent subchannels which permits using a single rake receiver in thebase station 104.

In the above mentioned channel allocation scheme, radio resources areexpected to be allocated on an as-needed basis. However, considerationmust also be given to the fact that, in order to set up a new CDMAchannel, a given reverse link channel must normally be given time to notonly acquire code phase lock, but also to adapt its transmission to theproper power level. The present invention avoids the need to wait foreach channel to accomplish this each time that it is set up, by severalmechanisms which are described more fully below. In general, thetechnique is to send a maintenance signal at a sufficient rate for eachsubchannel even when it is in a standby mode; that is, even in theabsence of data traffic.

One objective here is to minimize the size of each time slot, which inturn maximizes the number of subscribers that can be maintained in anidle mode. The size, t, of each time slot is determined by the minimumtime that it takes to guarantee phase lock between the transmitter atthe subscriber unit and the receiver in the base station. In particular,a code correlator in the receiver must receive a maintenance or“heartbeat” signal consisting of at least a certain number ofmaintenance bits over a certain unit of time. In the limit, thisheartbeat signal is sent by sending at least one bit from eachsubscriber unit on each reverse link at a predetermined time, e.g., itsdesignated time slot on a predetermined one of the N subchannels.

The minimum time slot duration, t, therefore depends upon a number offactors including the signal to noise ratio and the expected maximumvelocity of the subscriber unit within the cell. With respect to signalto noise ratio, this depends onEb/(No+Io)where Eb is the energy per bit, No is the ambient noise floor, and To isthe mutual interference from other coded transmissions of the othersub-channels on the reverse link sharing the same spectrum. Typically,to close the link requires integration over 8 chip times at thereceiver, and a multiple of 20 times that is typically needed toguarantee detection. Therefore, about 160 chip times are typicallyrequired to correctly receive the coded signal on the reverse link. Fora 1.2288 MHz code, Tc, the chip time, is 813.33 ns, so that this minimumintegration time is about 130 μs. This in turn sets the absolute minimumduration of a data bit, and therefore, the minimum duration of a slottime, t. The minimum slot time of 130 μs means that at a maximum, 7692time slots can be made available per second for each phase coded signal.

Once code phase lock is acquired, the duration of the heartbeat signalis determined by considering the capture or locking range of the codephase locking circuits in the receiver at the base station. For example,the receiver typically has a PN code correlator running at the code chiprate. One example of such a code correlator uses a delay lock loopconsisting of an early-late detector. A loop filter controls thebandwidth of this loop which in turn determines how long the codecorrelator must be allowed to operate before it can guarantee phaselock. This loop time constant determines the amount of “jitter” that canbe tolerated in the code correlator, such as about 1/8 of a chip time,Tc.

In the preferred embodiment, the system 100 is intended to supportso-called nomadic mobility. That is, high mobility operation withinmoving vehicles typical of cellular telephony is not expected to benecessary. Rather, the typical user of a portable computer who is activeis moving at only brisk walking speeds of about 4.5 miles per hour(MPH). At 4.5 MPH, corresponding to a velocity of 6.6 feet per second, auser will move 101 feet in 1/8 of the 1/1.2288 MHz chip time (Tc).Therefore, it will take about 101 feet divided by 6.6 feet, or about 15seconds for such a user to move a distance which is sufficiently far forhim to a point where the code phase synchronization loop cannot beguaranteed to remain locked. Therefore, as long as a completesynchronization signal is sent on a given reverse link channel every 15seconds, the reverse link loop will therefore be maintained. Inpractice, it is preferred not to push this to the limit, and asynchronization heartbeat signal is sent every several seconds.

FIG. 4 is a state diagram showing a set of operations performed by thebase station 170 and subscriber units 101. The sequence of statesentered into by the base station 170 are generally illustrated on theleft hand side of the figure, and the sequence of states for thesubscriber unit 101 on the right hand side.

In a first state 400, the subscriber 101 is initialized such as byturning on its battery power. The subscriber unit 101 then sends aninitialization message to the base station 170. In this initializationstate 402, the subscriber performs system determination, pilot channelacquisition, sync channel acquisition, and other timing functions asspecified, for example, by the IS-95B air interface standard. In effect,subscriber 101 determines the type of system in which it is operating,for example, a dual mode CDMA or analog mode, acquires acquisition onthe pilot channel by synchronizing its timing circuits, and also does asimilar timing function on the sync channel. In addition, an initialdefault open loop reverse power level may be determined such as bymeasuring a power level received on a forward link, as is known in theart. If the subscriber 101 can perform all of these tasks within acertain specified period of time, then it may successfully enter astandby mode state 403.

After it is initialized, the subscriber unit 101 may inform the basestation 170 of its successful completion of such tasks by sending aninitialization message 430 to the base 170. The base station 170 thenenters a state 451 where it allocates a reverse link maintenance channelto the particular subscriber 101. This can be done after acknowledgingpilot and synchronization, by sending a code phase p and time slot s tobe used for this particular subscriber unit in a message. Such a messagemay be, for example, sent on the forward link paging channel which thesubscriber unit 101 continues to monitor during the standby mode state403.

Also while in the standby state 403, once an open loop power level isset, the subscriber 101 periodically enters a state 404 in which aheartbeat message is sent to the base station 170 over the reverse link.

Once the base station 170 receives such a heartbeat message, it enters astate 452 in which it determines a link quality metric for the reverselink signal received from the subscriber unit 101.

Next, in state 454, this reverse link quality metric is sent as a linkquality report (LQR) message over the reverse link to the subscriberunit 101. The LQR message is sent over a paging or sync channel since notraffic channel is available during the standby mode.

The LQR may, for example, contain eight (8) bits of information. Thelink quality metric may be a bit error rate, a noise energy levelexpressed as E_(b),/N₀₁, or a power level.

Upon receiving the LQR, subscriber unit enters state 406 in which itcalculates its reverse power level using the received LQR and otherinformation.

The subscriber unit then continues to iterate through states 404 through407 in order to maintain an appropriate power level while in standbymode, until the subscriber unit receives a message indicating that it isto enter an active mode or otherwise leave standby mode.

Similarly, on the base station side, states 452, 454, and 456 arerepeated for each of the standby subscriber units while it is in theidle state.

The heartbeat signal 435 is sent via a synchronization message on theassigned maintenance channel at a data rate which need only be fastenough to allow the subscriber unit 101 to maintain synchronization withthe base station 170. The duration of the heartbeat signal is determinedby considering the capture range of the code phase locking circuits andthe receiver circuits and the base station 170.

In a preferred embodiment, the system is intended to support so-callednomadic mobility. That is, the relatively high mobility operation suchas within moving vehicles typical of cellular telephony is not expectedto be encountered. Rather, the typical user of a portable computer isexpected to remain connected only when moving about at brisk walkingspeed at about 4.5 miles per hour. In this situation, a user will moveapproximately 100 feet and 1/8 of the chip time at 1.2288 MHz.Therefore, it takes about 100 feet divided by 6.6 feet or about 15seconds for such a user to move a distance which is sufficiently far toa point where a code phase synchronization cannot be guaranteed.Therefore, as long as a complete heartbeat signal and power control wordfor a given reverse link channel are exchanged every 15 seconds, thereverse link will remain at the closed loop power level desired.

For further information concerning the arrangement of the heartbeatsignal, please refer to a co-pending patent application entitled “FastAcquisition of Traffic Channels for a Highly Variable Data Rate ReverseLink of a CDMA Wireless Communication System,” filed on Jun. 1, 1998,given Ser. No. 09/088,413, now U.S. Pat. No. 6,222,832, and assigned tothe same assignee of the present invention, the entire contents of whichare hereby incorporated by reference.

It can now be understood how the present invention implements closedloop power control in a code division multiple access system thatdynamically assigns reverse link traffic channels, even when suchtraffic channels are not allocated. This is accomplished by the basestation determining link quality measurement based on a reverse linkreceived signal that is received in response to maintenance heartbeatsignals. The heartbeat signals are sent in a rate which is onlysufficiently fast to maintain code phase lock. In response to this, alink quality report message is sent back to the subscriber unit on theforward link, such as on a paging or sync channel.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

For example, instead of ISDN, other wireline and network protocols maybe encapsulated, such as Digital Subscriber Loop (xDSL), Ethernet, orX.25, and therefore may advantageously use the dynamic wirelesssubchannel assignment scheme described herein.

Those skilled in the art will recognize or be able to ascertain using nomore than routine experimentation, many equivalents to the specificembodiments of the invention described specifically herein. Suchequivalents are intended to be encompassed in the scope of the claims.

What is claimed is:
 1. A subscriber unit comprising: circuitryconfigured to transmit first traffic data to a base station; wherein thecircuitry is further configured to receive control information; whereinin response to the subscriber unit not having traffic data to send tothe base station, the subscriber unit periodically transmitting a singlecode channel without traffic data in time intervals; wherein the periodfor transmitting the single code channel is determined from the receivedcontrol information; wherein the circuitry is further configured toreceive power commands in response to the transmitted single codechannel and adjust a transmission power level of the transmitted singlecode channel in response to the received power commands; wherein thecircuitry is further configured to transmit second traffic data to thebase station after periodically transmitting the single code channel;wherein a transmission power level of the transmitted second trafficdata is based on the power commands received in response to the singlecode channel.
 2. The subscriber unit of claim 1 wherein each timeinterval is at least one time slot.
 3. The subscriber unit of claim 1wherein the transmitting second traffic data is in response to receivinga grant from the base station.
 4. The subscriber unit of claim 1 whereinthe transmitting first and second traffic data is substantiallycontinuous.
 5. A method comprising: transmitting, by a subscriber unit,first traffic data to a base station; receiving, by the subscriber unit,control information; in response to the subscriber unit not havingtraffic data to send to the base station, periodically transmitting, bythe subscriber unit, a single code channel without traffic data in timeintervals; wherein the period for transmitting the single code channelis determined from the received control information; receiving powercommands, by the subscriber unit, in response to the transmitted singlecode channel and adjusting, by the subscriber unit, a transmission powerlevel of the transmitted single code channel in response to the receivedpower commands; transmitting, by the subscriber unit, second trafficdata to the base station after periodically transmitting the single codechannel; wherein a transmission power level of the transmitted secondtraffic data is based on the power commands received in response to thesingle code channel.
 6. The method of claim 5 wherein each time intervalis at least one time slot.
 7. The method of claim 5 wherein thetransmitting second traffic data is in response to receiving a grantfrom the base station.
 8. The method of claim 5 wherein the transmittingfirst and second traffic data is substantially continuous.